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Category Archives: Stata
Empower “and” and “or” in IF statement in Stata
Stata is a little bit awkward when using and and or in if statement, compared to SAS. For example: In SAS, we can write if 2001 <= fyear <= 2010. But in Stata, we usually write: if fyear >= 2001 … Continue reading
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Display mean and median test results in Stata
Sometimes we may want to produce the following table to compare the mean and median of two groups: First of all, please refer to this post to see Stata commands to test equality of mean and median. However, it is … Continue reading
Stata commands to do Heckman two steps
We often see Heckman’s two steps in accounting literature. But how to do it in Stata? The two steps refer to the following two regressions: Outcome equation: y = X × b1 + u1 Selection equation: Dummy = Z × … Continue reading
Stata commands to test equality of mean and median
Please read this post for how to display the results in a readyforuse format. UCLA IDRE has posted an article (link) that may provide a bit more explanation. UCLA IDRE is a great resource for learning statistical analysis. A big thank you … Continue reading
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Stata command to display combined Pearson and Spearman correlation matrix
Oftentimes we would like to display Pearson correlations below the diagonal and Spearman correlations above the diagonal. Two builtin commands, pwcorr and spearman, can do the job. However, we have to manually combine Stata output tables when producing the correlation table … Continue reading
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Stata command to convert string GVKEY to numerical GVKEY or vice versa
The default type of GVEKY in Compustat is string. Sometimes, we need it to be a numerical type in Stata (e.g., when we want to use the super handy command tsset). The command to convert string GVKEY to numerical GVEKY … Continue reading
Stata command to calculate the area under ROC curve
If we want to evaluate the predictive ability of a logit or probit model, Kim and Skinner (2012, JAE, Measuring securities litigation risk) suggest that A better way of comparing the predictive ability of different models is to use the Receiver … Continue reading
Stata commands to calculate skewness
Suppose we are going to calculate the skewness of 12 monthly returns. The 12 returns may be stored in a row (Figure 1) or in a column (Figure 2). This post discusses how to calculate the skewness in these two … Continue reading
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Commonly used Stata commands to deal with potential outliers
In accounting archival research, we often take it for granted that we must do something to deal with potential outliers before we run a regression. The commonly used methods are: truncate, winsorize, studentized residuals, and Cook’s distance. I discuss in … Continue reading
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Sample code for “outreg” command in Stata
outreg is a timesaving and musthave command in Stata. It will generate a readyforuse results table like this. I’m sure you will see what a relief this can give us. outreg is not a builtin command and can be installed … Continue reading
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